Oxy-fuel cutting torches discharge fuel gas and oxygen from a nozzle for cutting purposes. A typical torch includes a control body for being connected to separate fuel gas and oxygen supplies, tubes for supplying the oxygen and fuel gas from the control body to a head, and a cutting tip mounted to the head. The cutting tip receives the fuel gas and oxygen from the head and discharges these gases from its nozzle. More specifically, the head includes an interior surface extending around and defining a head cavity, an oxygen port that is open to the head cavity for supplying oxygen to the head cavity, and a fuel gas port that is open to the head cavity for supplying fuel gas to the head cavity. The cutting tip includes multiple passageways for directing the gases from the head to the nozzle.
Conventional torches first generate a preheat flame with gases discharged from the nozzle, and the preheat flame is used to heat a metal workpiece. After the preheat flame has heated the workpiece sufficiently, a high velocity cutting oxygen stream is activated and delivered through the nozzle. The high velocity cutting oxygen stream physically removes molten material of the workpiece by oxidation, to cut the workpiece. Typically, a number of valves and related components are provided upstream of the nozzle, such as in the control body, to control the operations of the cutting torch.
Flashback is a reaction caused in cutting torches by the reverse flow and ignition of the explosive mixture of gases used in the operation of the torch. Flashback typically originates at the nozzle of the torch and is often caused by an obstruction at this point, operator error, improper gas pressure and/or defective equipment. Due to the rapid and explosive nature of flashback, it poses a major safety hazard to the operator of the gas torch and can damage the gas torch and associated equipment. Accordingly, and as disclosed in U.S. Pat. Nos. 5,407,348 and 5,470,227, it is common for flashback arrestors constructed of sintered material to be used at the entry point of the gases into the torch. Whereas this stops the flashback from traveling upstream from the torch into the gas hoses, regulators and cylinders that supply the gas to the torch, it disadvantageously does not eliminate the effects of flashback within the torch itself, which means that the torch can be damaged or the operator can be injured by flashback within the torch.
It is also known to install packing material into the head of a torch or in a tube that is immediately upstream from the head for arresting flashback, as respectively disclosed in U.S. Pat. Nos. 1,176,017 and 1,290,422. It is common for this packing material to become damaged, such as by becoming clogged with carbon deposits resulting from flashback. As a result, the packing material must be periodically replaced. Disadvantageously, the removal and replacement of packing material in cutting torches is labor intensive. Additionally, and of significant safety importance, if the packing material is not properly packed it may not perform its intended function, which can result in damage to the torch or injury to its operator.
It is also known for the few gas-carrying passageways that are machined into cutting tips and cutting tip adapters to be shaped so that they have abrupt directional changes which are intended to restrict flashback, as is disclosed in U.S. Pat. Nos. 1,439,861; 3,746,500; 4,431,167 and 5,688,469. However, because there are constraints on the size of some cutting tips, it is common for the number of directional changes that can be efficiently provided by machining passages to be very limited. This limitation can in at least some situations disadvantageously limit the effectiveness of these types of adapters and cutting tips with respect to restricting flashback.
Accordingly, there is a need in the art for a flashback arrestor proximate the head of a cutting torch for restricting flashback into head, and which can be readily used and replaced in a manner that is likely to ensure satisfactory functionality of the flashback arrestor.